1. Field of the Invention
The present invention relates to a light composition of polyvinyl chloride resin and molded products thereof. More particularly, it relates to a polyvinyl chloride resinous composition comprising, as main ingredients, a polyvinyl chloride resin and a cellular filler and to molded products obtained by heating said composition at an increased pressure.
2. Description of the Prior Art
Polyvinyl chloride resins like vinyl chloride paste resins (hereinafter referred to as PVC resin) are normally in widespread use as a plastisol obtained by being mixed with a plasticizer, a stabilizer, pigments, fillers, diluents and the like, or as an organosol by being mixed with a plasticizer, a stabilizer, a solvent and the like.
Conventionally, these PVC plastisol and organosol exhibit a specific gravity of 1.0 or more and an average specific gravity of about 1.2, when such a PVC resin with a specific gravity of about 1.4 and a plasticizer with a specific gravity ranging from about 0.9 to about 1.0 are used.
In recent years such a plastisol and an organosol are widely used in a variety of fields including walls, floor and table coverings, book covers, decorative containers, upholsteries, automobile interiors, toys, leathers, sealants, sails, crown caps and the like.
In the field of floor coverings, however, as backings for floor coverings, asbestos papers, or glass fibre non-woven fabrics impregnated or coated with a PVC paste sol, or non-woven fabrics of glass fibres or synthetic fibres such as polyester and nylon impregnated or coated with such as SBR and polyvinyl alcohol have been used. Among those, backings of asbestos papers exhibit an exceedingly high percentage but there are included numerous problems and deficiencies including public hazards and a danger to heath recently presented, peeling off at the time of re-covering, waste disposal of used floor coverings, and a fatal defect that when applied to the floor bending toward the inside at an angle greater than 90 degrees, backings are broken though the upper portions of floor coverings themselves can stand, to thereby decrease the commercial value dreadfully. Moreover the floor coverings themselves are water-proof, but the backings of asbestos papers are inferior in water-proof property with a result that a range of fields usable is unavoidably limited. In view of the foregoing numerous drawbacks, there is a strong need for floor coverings eliminating such drawbacks.
Although, on the other hand, glass fibre or synthetic fibre non-woven fabrics, those coated or impregnated with a PVC plastisol, or those to which sheets of plasticized plastics having a thick tissue construction containing a filler in large quantities are joined as disclosed in the Japanese Patent Examined Publication No. 41848/1972 are, in fact, improved in many respects as compared with asbestos papers, the glass fibre non-woven fabrics expose glass fibre per se to thus adhere to workers and stab them in the skin while applied or transported. Further those are also weak in bending strength, to thus result in a decrease in commercial value. The backings such as those disclosed in the Japanese Patent Examined Publication No. 41848/1972 or non-woven fabrics coated or impregnated with a PVC plastisol, though improved in respects of stab in the skin, bending strength, peeling off and the like, still possess adhesiveness peculiar to the PVC plastisol and are heavy in weight, and accordingly difficult to handle especially at the time of transportation and application. Furthermore those coated or impregnated with the PVC plastisol have a difficulty in bonding when applied to the floor, and can only be applied by the selection of limited kinds of adhesives, which is a defect peculiar to a plasticized PVC resin. Eventually in some instances, those are applied to the floor by bonding thereto victria lawns and synthetic fibre non-woven fabrics and the like in order to improve such deficiencies.
In an attempt to save the weight of the PVC sol, foaming processes, either by mechanical or by chemical, have been proposed. According to those processes, notwithstanding that lightening of molded products is assuredly achieved in the long run, compressive elasticity, tensile strength, tear strength and dimensional stability are drastically reduced, hence being not satisfactory in practical usefulness.